Cape Breton’s Iona was the site of an unusual gypsum quarry and mill in the early 1900s.

Iona Gypsum Products Company ran the operation at Grass Cove, two miles north of Iona on the shore of the Bras d’Or Lake in Victoria County. The place name was reportedly changed to Gypsumville around that time but the new name didn’t stick.

The quarry’s working face, which was about 500 feet from the mill, extended 600 feet and averaged 25-30 feet in height.

Holes were drilled in the gypsum with hand augers and 40% dynamite was inserted to blast the rock. (Dynamite is usually rated by its nitroglycerine content so 40% dynamite contains 40% nitroglycerine.)

Blasted gypsum was sledge-hammered when necessary to make it “man-size” - a standard historical size meaning a rock an average-sized man could carry (i.e. about the size of a basketball). The term was a unit of measurement in the gypsum industry and it’s still used in some places to describe the size of stones used in landscaping (i.e. a one-man rock, a two-man rock, etc.).

The fines (smaller pieces of blasted gypsum) were loaded onto the carts with “forks” (i.e. pitch forks).

The broken gypsum was hauled in one-ton, horse-drawn cars on tracks laid to different parts of the quarry. On arrival at the mill, the cars were pulled up an incline and dumped into a bin over the crusher that broke the rock down to smaller pieces.

A spur rail line owned by the company connected the quarry and mill to the Canadian National Railway. The company also had a wharf adjacent to the quarry for exporting the plaster and for bringing in coal. Horses pulled the loaded cars from the mill to the wharf.

Somewhat unusually for Nova Scotia, the Grass Cove quarry did not export raw gypsum but instead calcined the gypsum and manufactured it into plaster products before export. (Calcining gypsum means to heat and partially dehydrate it. It's part of the process of turning gypsum into plaster so it can be used in products like wallboard, mouldings and casts.) The Grass Cove mill had two calcining kettles that could process a total of 50 tons of gypsum per day.

Most Nova Scotia gypsum has not been calcined before being exported because it has usually made more economic sense to do the calcining where the gypsum is manufactured into plaster or wallboard, and closer to the major markets where most of it is sold. In 1915, there were seven gypsum companies operating in Nova Scotia but the Grass Cove quarry and the Windsor Plaster Company were the only two that had calcining plants. (See the story of the Windsor Plaster Company, and more info about how gypsum was processed, at (

We are sometimes asked why Nova Scotia still exports raw gypsum instead of manufacturing a product like wallboard here. The answer is that while some small-scale manufacturing of wallboard and plaster has been done in Nova Scotia, there is generally not a business case for doing that manufacturing so far from major markets, especially since it is so much easier to ship raw gypsum than finished products which are more likely to be damaged in transport.

This issue was laid out by a French consulting engineer named Jules Deschamps who visited the Grass Cove quarry in November 1926. He wrote a lengthy memo afterwards, likely for a company that was considering buying the operation, but the memo’s purpose is not stated. In it, Deschamps argued that the quarry would be more profitable as a larger, more efficient exporter of raw gypsum, like most other Nova Scotia gypsum quarries, instead of continuing to produce manufactured plaster for export.

Deschamps said that calcined plaster, “naturally spoiling in dampness, can only be carried in barrels, or in sacks if the distance is not too great and the transportation is made in closed cars….barrels are expensive. They add their weight [to the shipment]. They are cumbersome, not always very water-tight. In short, the carriage of the finished product is more difficult.”

Deschamps said manufacturing plaster and selling it locally would make sense (although its success would be limited by the size of the local market), as would selling raw gypsum to distant customers. This would give the company “two different and clearly distinct groups of customers. The operator would not compete with his own customers.”

However, the Iona Gypsum Products Company’s business model of shipping finished plaster products to distant customers was, in a sense, the worst of all worlds. It created the expense and challenges of shipping, while also potentially creating competitive issues with the American plaster companies that were based in the markets where the plaster was being sold.

Deschamps pointed out that “almost all the gypsum development in Nova Scotia belongs to American concerns which export raw gypsum and work it themselves in the United States. If there was an advantage in working it at the quarry these concerns would certainly do so.” He also said that by shipping raw gypsum, “Waste and losses on the way would be avoided.”

Deschamps did an analysis of the Iona company’s financials, which, he said, “do not seem to have been brilliant.” Its 1925 balance sheet showed a profit of only $2,367.63, but Deschamps said the statements did not include expenses such as interest, and that the company was, in fact, losing money. He said, “the gypsum business of the Iona Gypsum Products cannot really be considered as a going concern.” Indeed, the Iona Gypsum Products Company would shut down just a few years later.

While most Nova Scotia gypsum is used in wallboard today, Deschamp’s analysis is still largely true a century later. Shipping a finished product, like wallboard, longer distances increases the amount that will break or spoil. It is much easier to ship raw gypsum to major wallboard plants in the US that are closer to market. This business model has created a huge number of jobs for Nova Scotians since the 1770s when farmers in Hants County first extracted gypsum on their farms and sold it for export, to be used as fertilizer in the United States.

Deschamps cited a Mr. John Kindley, who estimated that the Grass Cove quarry had about 25 million tons of gypsum available for extraction, a very significant amount given that the quarry extracted fewer than 10,000 tons almost every year it operated. Deschamps suggested the quarry could produce tens of thousands of tons per year if its business model were changed and capital improvements were made, such as installing aerial cable cars to haul gypsum from the quarry to the mill, replacing the horse-drawn cars.

The operation’s main products were plaster of Paris delivered in 320- or 245-pound barrels, plaster mixed with fibre or hair (to strengthen the end product) in 50-pound “paper sacks,” stucco in sacks of 100 pounds and plaster for dentists (i.e. moulds) in 100-pound barrels.

Over the course of its life, the operation sent plaster to the other Atlantic provinces, Quebec, Ontario, New Zealand, Australia and New York.

The Grass Cove quarry operated continuously from 1914-32 except for 1918 when it was shut down, perhaps due to WWI when many mines and quarries struggled with lack of labour and supplies.

The quarry was ultimately a victim of the Great Depression. It shut down in 1932 and was sold to the Canadian Gypsum Company. It never operated again.

Grass Cove produced a total of 105,283 tons of gypsum. The number of men it employed each year averaged about 28 over its life, with a low of seven men in 1922 and a high of 48 in 1931.

Less is known about a second quarry in the Iona area, which was in Plaster Cove, 1.5 miles south of Grass Cove, and about half a mile north of Iona. The Cape Breton Gypsum Company operated the Plaster Cove quarry, which had a working face 100 yards west of the mill that was 30 feet high and 100 feet long. The gypsum was hauled from the quarry to the operation’s mill in carts.

At the Plaster Cove mill it was crushed, calcined and made into plaster – perhaps proximity to the Grass Cove operation made the Cape Breton Gypsum Company want to compete by producing plaster, not just raw gypsum.

A 1929 report said the Plaster Cove quarry had been idle for “several years.” Since Deschamps did not comment on it, it is likely that the Plaster Cove quarry was shut down before his 1926 visit to the area. (We can safely assume he would not have approved of it producing plaster for export!)